Goodwill and other intangible assets - Schedule of Goodwill (Details) $ in Millions	9 Months Ended
May 31, 2017 USD ($)
Goodwill [Roll Forward]
Net book value - Beginning Period	$ 15,527
Acquisitions	87
Currency translation adjustments	(98)
Net book value - Ending Period	15,516
Reportable Segments \| Retail Pharmacy USA
Goodwill [Roll Forward]
Net book value - Beginning Period	9,036
Acquisitions	87
Currency translation adjustments	0
Net book value - Ending Period	9,123
Reportable Segments \| Retail Pharmacy International
Goodwill [Roll Forward]
Net book value - Beginning Period	3,369
Acquisitions	0
Currency translation adjustments	(36)
Net book value - Ending Period	3,333
Reportable Segments \| Pharmaceutical Wholesale
Goodwill [Roll Forward]
Net book value - Beginning Period	3,122
Acquisitions	0
Currency translation adjustments	(62)
Net book value - Ending Period	$ 3,060

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=64834752&loc=SL49117168-202975

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- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

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- Definition

Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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